The extensive use of personal computers and other data processing facilities at home and in the office gave rise to a need for voice and data transmission and switching capabilities on a wide spread basis. To satisfy this need, the integrated services digital network (ISDN) providing approximately 144 kilobits per second bandwidth was developed for use by telecommunications subscribers. The continuing growth of digital services and capabilities has now created a need for packet transmission and switching arrangements which have the capacity for larger bandwidths. In response to this need for higher information bandwidths, a new capability known as broadband ISDN (B-ISDN) is being developed to provide bandwidths on the order of 150 megabits per second.
The prospect of a 150 megabit per second channel to multitudes of residential and business customers has caused system planners to seek new revenue generating services which can use the bandwidth. One such desirable service is the delivery of full motion video, e.g. television, to B-ISDN customers. Packetized television signal delivery requires a bandwidth of approximately 45 megabits per second which is well within the B-ISDN capacity, however television signals are not bursty like computer data but are substantially continuous. Relatively few video channels can be presented continuously to customers over a single 150 megabit per second B-ISDN connection.
Video service can be provided to B-ISDN customers by selectively connecting one of many video sources to a single video channel conveyed to those customers. In this way a single 45 megabit per second video channel on a B-ISDN link can deliver many different television programs to a customer, one at a time. An arrangement is needed however, to provide the necessary selective connections between the video sources and B-ISDN video channels on customer access lines.
In one packet switching arrangement, as described in the co-pending application Johnson-Spanke, customer access lines are connected to a broadband packet network which provides selective packet connections among B-ISDN customers connected to the access lines. The arrangement described in the Johnson et al., application can be extended to provide selected video connections by attaching video sources as inputs to the same broadband packet network which provides broadband packet connections among the B-ISDN customers. Although the use of the broadband packet network provides the ability to selectively connect packets from the video sources to customer access lines, it is very inefficient.
Packet switching networks are designed, and their efficiency maximized for the selective connection of bursty data. Efficiency is achieved by sharing network capacity among users when some users have information to send and others do not. In the case of relatively continuous high bandwidth data such as video signals network bandwidth is continuously used and is not available for sharing. Accordingly, a significant number of video channels through a broadband packet network can use up the network's capacity to transmit other information. The use of a packet network to switch both video and non-video packets results in blocking by the packet network of non-video packets, due to network capacity limits or in the use of a packet switching network with far greater capacity (and greater expense) than would be needed to efficiently deliver the non-video packets among the customers.
A need exists for a packet switching arrangement which can efficiently connect packets among customers connected to a plurality of customer access lines while at the same time selectively delivering broadband video packets to the customers via the same customer lines.